Process of producing pulps containing rubber substances



Patented 01.T13, 1936 PROCESS or 'rnonncme PULPS me RUBBER snnsrancn 2,057,33 oFFm gom-sm- ,Harry 0. Fisher, 01110131111111, and GeorzeAcus,

Arlington Heights,

Richardson Company, Looklan poration oi'flhio No Drawina'. Application Serial No. 618,016

like.

These process steps are valuable in. any in-- stance where it is desired to make intimate association between anon-solid substance and a' fibrous material.

Our present invention deals vvith discoveries made by us whereby we form a preliminary aspart to include such statements otherwise in this specification.

formed into a paper nilll pulp; Alarge variety or novel materials c n be made ject matter to set a It is our primary discovery that if rubber latex t V .The heater operation is to The d, Qhio, a coro. minim-s June 18,1932,

using this pulp, which have valuable characteristics.

In the following description we will'flrst desurprising' and very ourdiscoveries. There is no intent in this sublimit or bounds to our-invention.

Referring first to our process using ordinary 1 solids conwarm W. P. mixer whereby mixing is carried out beater.

but care must be taken that the beating time be her, there is,

over, but are appreciable even at lower able, and where temperature, say, to possible, since higher temperatures accelerate the bringing away of the rubber from the fiber. The adverse conditions noted hold true, especially when the rubber content is high, say, 25% or percentages.

The mechanism for carrying out this mixing process must permit the associating of the fiberswith the latex at comparatively low temperatures so that the rubber is not precipitated prematurely, and then means must be employed to remove enough preservative to set the rubber on to the fibers. This requires that if one W. P. mixer is used and the elimination oi is done by heat, it must be provided with means for rapid heating or cooling to take care of the two stages of the process. On the other hand, if the preliminary association of ingredients is made in one mixer which always is kept cool, a more practical process is obtained.

beincorporated is low enough to be absorbed substantially completely into the fibrous matter so that there are no free liquids to run out of the mass, then the use of such a mixer is advantageous since bulky well-felted fibrous material, such as chemical paper pulp, can be broken down largely into individual fibers and can be thorou'ghly impregnated with the solutions of latex in the first stage of the operation in the Banbury, whereupon they then can be transferred to a secondary mixer of the W. P. type, which always is kept hot where the ammonia preservative can be eliminated, the rubber set on the fibers and v the pulp broken down ready for the beater treatment.

The above descriptions have been based upon the use of a normal latex oi commerce containing about. 38% rubber solids. Latices oi other concentrations and of substances other than rubber, such as balata or gutta percha can be used to gain certain special results or achieve economy in operation, as desired. Speaking particularly 0! rubior example. the material controlled by Jeavons, Tinto & Co., 'Ltd., London, England, known as "Jatex", which contains about 60% rubber solids by weight, and is a thick, creamy, white liquid. Speaking of concentrated latices, generally, it is stated thatin some processes 0! concentrating the normal latex irom rubber trees to high rubber contents, many of the water soluble and undesirable resinous substances naturally associated with rubber have been eliminated, and hence a better product can be made from the concentrated latex.

Another brand of concentrated latex is sold in the United States under the name of "Revertex and contains up to 75% rubber content. This material is a very thick, white, creamy paste and is shipped in iron drums or round paper containers. Another series of latices is sold in the United States under the name of Lotols; these can be purchased in various concentrations- 1M ex- -ample, 32% and 60%. Still another type of latexgoes under the name of Vuitex and the rubber in it exists in a pre-vulcanized rorm.

--When the rubber from this latex is set by any oi the methods with which it is used. the rubber already is vulcanized.

-Rubber bearing pulp' prepared by the above method is to be used by any of the well known 4 paper making processes-tor example, cylinder machines, Fourdrinier degrees I". or lower it machines, wet lap ma' chines, pulp forming mold process, etc. The ordinary Jordaning, diluting, beating, concentrating processes are to be employed. To gain certain special results premixed pulp of other materials can be incorporated with a latex pulp in the mixers, the heaters, the chests, the vats, etc. For example, a pulp was prepared according to the teachings of Stevenson and Buron in United States Patent No. 1,771,150, or an asphalt, having a penetration at 77 degrees F. of 1 and a ball and ring melt point 0! 195 degrees F., with 50% unbleached sulphite. by weight were used oi each material. In a separate operation a pulp was prepared or parts of sulphite,

278 parts concentrated ammonia solution, and 2'78 parts of latex solution containing 38% solids. These two pulps were mixed together and refined in a beater at substantially room temperature, formed intosheets and dried in an oven. The result was a sheet of paper deep black in color, more or less glossy on the outside and a lighter brownish-black color uniform on the inside. This sheet of paper combined the stifiness or a hard asphalt with the flexibility of the rubber ingredients, which properties were added tothe natural body imparted by the sulphite.

Similarly, a composite pulp made from two mixes, the one containing sulphite and the rubher from. latex, and the other sulphite and a polymerized rubber resin, known as Davex", formed into sheets and dried in an oven, gave products with dark brownish exteriors and lighter brown interiors, which sheets were stifi and yet possessed considerable resiliency and had a peculiar waxy and rubbery Ie'el.

In a similar manner pulps of natural and artificial resinous materials, waxes, gums, and

the like, can be intermixed with the rubber pulp results. If desired, in o! the ingredients can tomaeeous earth, or coloring matter such as iron oxide, chromicoxide, etc., or starchy matters or various other ingredients used in paper making, may. be employed along with the latex pui p or the latex pulps modified by other. ingredients, said substances beater or similar place, orporated along with the other ingredients in the mixer as conditions permit. Paper dyes for modifying the color oi. the sheets can be employed in the well known manner. Vulcanizing agents for being added to the pulp in the they can be incor throughout the rubber can be incorporated at that point in the process which gives the best results, which ordinarily will be in the mixer where the rubber is laid downon the fibers. Thus, ammonium polysulphide has been added to the mixer and vulcanization at 100 lbs. steam pressure in a fiity ton press, has been successful.

A description now will be given oi typical rubber/sheets. prepared by the above methods with latex of 38% consistency alone. Such a sheet of 42 points 'taining 10% bleached sulphite showed, for a caliper of 17' contained 50% rubber and 50% sulphite and calipered .0265, was translucent to strong daylight, had a brownish rubbery color, had a good "rattle", a Mullen test of 85 pounds per square inch, and-an Elmendori' tear test of 176 units. A sheet-from the samemix with a caliper inch and an Elmendorf tear test of Sheets made in the same way condry rubber from latex and 90% unpounds per square test of 520-pounds per square inch. The-tear test could not be determined since the sheet was too strong. An outstanding characteristic of the 2% product was its great stillness. 'As the percentage of rubber in.the sheet decreases',-say, from 59 down to 2, the sheet becomes less and less translucent. Upon passing the 2% sheet through the bottom nip of a set of heavy board machine calenders, seven rolls high, the sheets took on the fibers.

for a brief an extremely high We have discovered that if moist sheets containing fiber and rubber are subjected to pressure period, that the qualities of the final dried product are improved both in stillness and otherwise; This discovery has application not only -to our particular pulp, but to latex sheets formed by chemical precipitation of rubber on For example, we have found that it is sumcient to fifteen pressure to the square inch.

We do not limit our invention to the use of ammonia as an anti-precipitant. There is no quality of ammonia other than the one described which is or use, except that it is volatile. 'We

might use some other preservative duringthe preliminary association and then inhibit its action by. changing it chemically. We might do this with the ammonia for that matter. There is value, however, we believe, in using a volatile anti-precipitant because it is easy to gradually evaporate it from the preliminary mixture.

Our work with the rubber pulp has developed that small proportions of rubber with fibers in stable association mixed with carton or box, board box board may be used of much pulp will greatly enhance the physical properties of carton or box board made therefrom. Such would otherwise-be required, and thus we believe that. our discovery has wider application so far as product is concerned, than the product of our process. Thus, precipitation of latex rubber in a beater, as has been attempted in the past, will probably in box and carton stock that we have observed, particularly where w'et pressing is used.

The proportions of anti-precipitant do not seem to be critical. For example, good quality pulp was made with the use of monia solution of 29% pounds 01' latex (38% solids) precipitated onto pounds of sulphite pulp (bone-dry weight).

showed a-Mullen test of pounds vher) test of 176 units.

gloss but darkened ,in color.

ing a pulp by further mixing with to submit the moist sheets to a tensecond pressing at-about 30 poundsdevelop some of the valuable properties only 20 pounds of am NH: concentration, to 3'12 1. An uncured, vulcanizable sheet made ,on

equipment for felting fibers from pulp and susceptible of molding under heat andpressure to form her] or even ebonite (completely vulcanized rub- 2. A paper mill rubber and fiber, or with certain liners of rubber and fiber, and others of bitumen or resin (natural or artificial) and fibers, with'various kinds-of fibers. suitable for embossing and lacquer, for autom the like. 3. Apapermill product suitable for being in: corporated into rubber belting.

4. A new kind of roofing sheet.

5. A new kind of paper board for certain kinds of cartons, ii desired greaseprooi', and highly fiex ible, resilient under stiff and strong, etc.

Having thus set forth our teaching by reference to our discoveries and certain practices following them, we. claim the following as our invention:

1. That process which consists in mixing together rubber latex, ammonia solution, and

fibrous materialwithout evaporatingv the am- -monia, until the mixture is complete, then furpresen'ce of heat to evaporate 3'5 ther mixing inthe the' ammonia and set'the rubber, and then formwater, for the purpose described, and, in a beater or suitable paper mill apparatus, diluting and mixing said pulp with other pulp forming materials, and passing the resulting material over a paper machine,

said diluting and mixing taking place at room products producedvarious items now made of vuicanized'rubproduct made completely of or other heat plastic materials,

decorating, as'with paint orbile tops, wall hangings, and

cold conditions, extremely v temperature or below, for the purpose described. 2. A process of producing pulps containing rubber substance, .comprising first; depositing the rubber substance on the fibers by mixing a mass of the fibers and rubber sustance while the mass is substantially less mobile than is required for final pulping, and whileretar ins precipitation precipitation of the continuing the mixing with the addition of water sufilcient' to disperse the fibers, with their preformed coating or rubber substance, to that degree required for forming'the pulp into a sheet on a paper making machine, the rubber substance-being derived from latex. the precipitation being retarded by ammonia in quantity equal to a major portion of the latex, and the efi'ec'tive precipitation being brought about by raising theof the rubber substance, then permitting efi'ective rubber substance and. finally substantialagglomeration of v 

